The invention relates to a pressure-sensitive switch, comprising: an edge structure extending in a substantially closed contour; a first carrier which is connected on its edges to the edge structure and which is electrically conductive on its side connected to the edge structure; a second carrier which is connected on its edges to the edge structure and which extends substantially parallel to the first carrier and is electrically conductive on its side connected to the structure; and connecting means for connecting the external connections to the first and the second carrier.
Such a switch is known from U.S. Pat. No. 5,818,002.
In this known switch the carriers are formed by relatively thick plates which are provided in their centre with an inward directed dimple. When pressure is exerted on the plates they will bend and move towards each other in the centre so that the dimples can make mutual electrical contact. It is possible to adjust the sensitivity of the switch by modifying the form and depth of the dimples.
This is however a switch of a rugged type which does not lend itself to miniaturization and which only operates properly when a force is exerted on the plates in the vicinity of the dimple.
The object of the present invention is to provide such a device which is suitable for miniaturization and which responds when a force is exerted at any random location on its surface.
This objective is achieved in that the distance between the carriers in their neutral position is substantially the same over the whole surface.
Owing to this uniform spacing between the carriers the switch is identical over its whole active surface, so that no local aberrations such as dimples have to be made. The switch can hereby be miniaturized more easily. This uniformity also ensures that the sensitivity of the switch is the same over its whole surface.
In order to also enable construction of the switch with a comparatively large surface area relative to the thickness, the carriers are preferably manufactured from foil, and spacers are placed between the carriers inside the edge structure, which spacers are fixed to each of the carriers.
The use of spacers makes the use of a flexible carrier possible. The switch can hereby also be made sensitive for a locally applied pressure.
In order to obtain a uniform sensitivity over the surface, the spacers are evenly distributed over the surface inside the structure.
In some situations it is attractive if the spacers are distributed in a pattern with varying density over the surface inside the structure.
The sensitivity can hereby be made location-dependent.
Other attractive embodiments are stated below.